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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr.instruct;
import net.sf.saxon.Controller;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.flwor.LocalVariableBinding;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.expr.sort.*;
import net.sf.saxon.functions.CollatingFunction;
import net.sf.saxon.lib.StringCollator;
import net.sf.saxon.lib.TraceListener;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.StandardNames;
import net.sf.saxon.pattern.PatternSponsor;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.Err;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.SequenceType;
import net.sf.saxon.value.StringValue;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
* Handler for xsl:for-each-group elements in stylesheet. This is a new instruction
* defined in XSLT 2.0
*/
public class ForEachGroup extends Instruction
implements SortKeyEvaluator, ContextMappingFunction {
public static final int GROUP_BY = 0;
public static final int GROUP_ADJACENT = 1;
public static final int GROUP_STARTING = 2;
public static final int GROUP_ENDING = 3;
private Expression select;
private Expression action;
private byte algorithm;
private Expression key; // for group-starting and group-ending, this is a PatternSponsor
private Expression collationNameExpression;
private int keyItemType;
private URI baseURI;
private StringCollator collator = null; // collation used for the grouping comparisons
private SortKeyDefinition[] sortKeyDefinitions = null;
private transient AtomicComparer[] sortComparators = null; // comparators used for sorting the groups
private LocalVariableBinding groupBinding = null;
private LocalVariableBinding keyBinding = null;
private boolean composite = false;
/**
* Create a for-each-group instruction
* @param select the select expression (selects the population to be grouped)
* @param action the body of the for-each-group (applied to each group in turn)
* @param algorithm one of group-by, group-adjacent, group-starting-with, group-ending-with
* @param key expression to evaluate the grouping key
* @param collator user for comparing strings
* @param collationNameExpression expression that yields the name of the collation to be used
* @param baseURI static base URI of the expression
* @param sortKeys list of xsl:sort keys for sorting the groups
*/
public ForEachGroup(Expression select,
Expression action,
byte algorithm,
Expression key,
StringCollator collator,
Expression collationNameExpression,
URI baseURI,
SortKeyDefinition[] sortKeys) {
this.select = select;
this.action = action;
this.algorithm = algorithm;
this.key = key;
this.collator = collator;
this.collationNameExpression = collationNameExpression;
this.baseURI = baseURI;
this.sortKeyDefinitions = sortKeys;
Iterator kids = iterateSubExpressions();
while (kids.hasNext()) {
Expression child = (Expression)kids.next();
adoptChildExpression(child);
}
}
/**
* Get the name of this instruction for diagnostic and tracing purposes
* @return the name of the instruction
*/
public int getInstructionNameCode() {
return StandardNames.XSL_FOR_EACH_GROUP;
}
/**
* Get the select expression
* @return the select expression
*/
public Expression getSelectExpression() {
return select;
}
/**
* Get the action expression (the content of the for-each-group)
* @return the body of the xsl:for-each-group instruction
*/
public Expression getActionExpression() {
return action;
}
/**
* Get the grouping algorithm (one of group-by, group-adjacent, group-starting-with, group-ending-with)
* @return one of group-by, group-adjacent, group-starting-with, group-ending-with
*/
public byte getAlgorithm() {
return algorithm;
}
/**
* Get the grouping key expression expression (the group-by or group-adjacent expression, or a
* PatternSponsor containing the group-starting-with or group-ending-with expression)
* @return the expression used to calculate grouping keys
*/
public Expression getGroupingKey() {
return key;
}
/**
* Get the primitive item type of the key
* @return the primitive item type of the grouping key
*/
public int getKeyItemType() {
return keyItemType;
}
/**
* Get the sort keys defined at the for-each-group level, that is, the keys for sorting the groups
* @return the definitions of the sort keys defined as children of the xsl:for-each-group element
*/
public SortKeyDefinition[] getSortKeyDefinitions() {
return sortKeyDefinitions;
}
/**
* Get the statically-allocated sort key comparators for sorting at the group level, if known
* @return the comparators used for comparing sort key values, one entry in the array for each
* nested xsl:sort element
*/
public AtomicComparer[] getSortKeyComparators() {
return sortComparators;
}
/**
* Get the statically-determined collator, or null if the collation was not determined statically
* @return the collation, if known statically, or null if not
*/
/*@Nullable*/ public StringCollator getCollation() {
return collator;
}
/**
* Get the static base URI of the instruction
* @return the static base URI if known, or null otherwise
*/
/*@Nullable*/ public URI getBaseURI() {
return baseURI;
}
public LocalVariableBinding getGroupBinding() {
return groupBinding;
}
public void setGroupBinding(LocalVariableBinding binding) {
groupBinding = binding;
}
public LocalVariableBinding getKeyBinding() {
return keyBinding;
}
public void setKeyBinding(LocalVariableBinding binding) {
keyBinding = binding;
}
public boolean isComposite() {
return composite;
}
public void setComposite(boolean composite) {
this.composite = composite;
}
/**
* Simplify an expression. This performs any static optimization (by rewriting the expression
* as a different expression).
*
* @return the simplified expression
* @throws XPathException if an error is discovered during expression
* rewriting
* @param visitor an expression visitor
*/
/*@NotNull*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
select = visitor.simplify(select);
action = visitor.simplify(action);
key = visitor.simplify(key);
if (collationNameExpression != null) {
collationNameExpression = visitor.simplify(collationNameExpression);
}
return this;
}
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
select = visitor.typeCheck(select, contextItemType);
ItemType selectedItemType = select.getItemType(th);
if (groupBinding != null) {
groupBinding.setRequiredType(SequenceType.makeSequenceType(selectedItemType, StaticProperty.ALLOWS_ONE_OR_MORE));
}
ExpressionVisitor.ContextItemType cit = new ExpressionVisitor.ContextItemType(selectedItemType, false);
action = visitor.typeCheck(action, cit);
key = visitor.typeCheck(key, cit);
if (collationNameExpression != null) {
collationNameExpression = visitor.typeCheck(collationNameExpression, contextItemType);
}
if (Literal.isEmptySequence(select)) {
return select;
}
if (Literal.isEmptySequence(action)) {
return action;
}
if (sortKeyDefinitions != null) {
boolean allFixed = true;
for (SortKeyDefinition sk : sortKeyDefinitions) {
Expression sortKey = sk.getSortKey();
sortKey = visitor.typeCheck(sortKey, cit);
if (visitor.getStaticContext().isInBackwardsCompatibleMode()) {
sortKey = FirstItemExpression.makeFirstItemExpression(sortKey);
} else {
RoleLocator role =
new RoleLocator(RoleLocator.INSTRUCTION, "xsl:sort/select", 0);
role.setErrorCode("XTTE1020");
sortKey = CardinalityChecker.makeCardinalityChecker(sortKey, StaticProperty.ALLOWS_ZERO_OR_ONE, role);
}
sk.setSortKey(sortKey, true);
if (sk.isFixed()) {
AtomicComparer comp = sk.makeComparator(
visitor.getStaticContext().makeEarlyEvaluationContext());
sk.setFinalComparator(comp);
} else {
allFixed = false;
}
}
if (allFixed) {
sortComparators = new AtomicComparer[sortKeyDefinitions.length];
for (int i=0; i< sortKeyDefinitions.length; i++) {
sortComparators[i] = sortKeyDefinitions[i].getFinalComparator();
}
}
}
keyItemType = key.getItemType(th).getPrimitiveType();
if (groupBinding != null) {
fixupGroupReferences(this, this, groupBinding);
}
return this;
}
private static void fixupGroupReferences(Expression exp, ForEachGroup feg, LocalVariableBinding groupBinding) {
if (exp instanceof GroupVariableReference && ((GroupVariableReference)exp).getBinding() == groupBinding) {
((GroupVariableReference)exp).setControllingExpression(feg);
} else {
for (Iterator iter = exp.iterateSubExpressions(); iter.hasNext();) {
Expression child = iter.next();
fixupGroupReferences(child, feg, groupBinding);
}
}
}
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
select = visitor.optimize(select, contextItemType);
ItemType selectedItemType = select.getItemType(th);
ExpressionVisitor.ContextItemType sit = new ExpressionVisitor.ContextItemType(selectedItemType, false);
action = action.optimize(visitor, sit);
key = key.optimize(visitor, sit);
adoptChildExpression(select);
adoptChildExpression(action);
adoptChildExpression(key);
if (Literal.isEmptySequence(select)) {
return select;
}
if (Literal.isEmptySequence(action)) {
return action;
}
// Optimize the sort key definitions
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
Expression sortKey = skd.getSortKey();
sortKey = visitor.optimize(sortKey, sit);
skd.setSortKey(sortKey, true);
}
}
if (collationNameExpression != null) {
collationNameExpression = visitor.optimize(collationNameExpression, contextItemType);
}
if (collator == null && (collationNameExpression instanceof StringLiteral)) {
String collation = ((StringLiteral)collationNameExpression).getStringValue();
URI collationURI;
try {
collationURI = new URI(collation);
if (!collationURI.isAbsolute()) {
collationURI = baseURI.resolve(collationURI);
final String collationNameString = collationURI.toString();
collationNameExpression = new StringLiteral(collationNameString);
collator = visitor.getStaticContext().getCollation(collationNameString);
if (collator == null) {
XPathException err = new XPathException("Unknown collation " + Err.wrap(collationURI.toString(), Err.URI));
err.setErrorCode("XTDE1110");
err.setLocator(this);
throw err;
}
}
} catch (URISyntaxException err) {
XPathException e = new XPathException("Collation name '" + collationNameExpression + "' is not a valid URI");
e.setErrorCode("XTDE1110");
e.setLocator(this);
throw e;
}
}
return this;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
SortKeyDefinition[] newKeyDef = null;
if (sortKeyDefinitions != null) {
newKeyDef = new SortKeyDefinition[sortKeyDefinitions.length];
for (int i = 0; i < sortKeyDefinitions.length; i++) {
newKeyDef[i] = sortKeyDefinitions[i].copy();
}
}
ForEachGroup feg = new ForEachGroup(
select.copy(),
action.copy(),
algorithm,
key.copy(),
collator,
collationNameExpression.copy(),
baseURI,
newKeyDef);
if (groupBinding != null) {
LocalVariableBinding lvb = groupBinding.copy();
feg.setGroupBinding(lvb);
ExpressionTool.rebindVariableReferences(feg, groupBinding, lvb);
}
if (keyBinding != null) {
LocalVariableBinding lvb = keyBinding.copy();
feg.setGroupBinding(lvb);
ExpressionTool.rebindVariableReferences(feg, keyBinding, lvb);
}
feg.setComposite(isComposite());
return feg;
}
/**
* Get the item type of the items returned by evaluating this instruction
*
* @return the static item type of the instruction
* @param th the type hierarchy cache
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return action.getItemType(th);
}
/**
* Compute the dependencies of an expression, as the union of the
* dependencies of its subexpressions. (This is overridden for path expressions
* and filter expressions, where the dependencies of a subexpression are not all
* propogated). This method should be called only once, to compute the dependencies;
* after that, getDependencies should be used.
*
* @return the depencies, as a bit-mask
*/
public int computeDependencies() {
// some of the dependencies in the "action" part and in the grouping and sort keys aren't relevant,
// because they don't depend on values set outside the for-each-group expression
int dependencies = 0;
dependencies |= select.getDependencies();
dependencies |= key.getDependencies() & ~StaticProperty.DEPENDS_ON_FOCUS;
dependencies |= (action.getDependencies()
&~ (StaticProperty.DEPENDS_ON_FOCUS | StaticProperty.DEPENDS_ON_CURRENT_GROUP));
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
dependencies |= (skd.getSortKey().getDependencies() & ~StaticProperty.DEPENDS_ON_FOCUS);
Expression e = skd.getCaseOrder();
if (e != null && !(e instanceof Literal)) {
dependencies |= (e.getDependencies());
}
e = skd.getDataTypeExpression();
if (e != null && !(e instanceof Literal)) {
dependencies |= (e.getDependencies());
}
e = skd.getLanguage();
if (e != null && !(e instanceof Literal)) {
dependencies |= (e.getDependencies());
}
}
}
if (collationNameExpression != null) {
dependencies |= collationNameExpression.getDependencies();
}
return dependencies;
}
/**
* Get the static properties of this expression (other than its type). The result is
* bit-signficant. These properties are used for optimizations. In general, if
* property bit is set, it is true, but if it is unset, the value is unknown.
*
* @return a set of flags indicating static properties of this expression
*/
@Override
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
p |= (action.getSpecialProperties() & StaticProperty.ALL_NODES_UNTYPED);
return p;
}
/**
* Determine whether this instruction creates new nodes.
* This implementation returns true if the "action" creates new nodes.
* (Nodes created by the condition can't contribute to the result).
*/
public final boolean createsNewNodes() {
int props = action.getSpecialProperties();
return ((props & StaticProperty.NON_CREATIVE) == 0);
}
/**
* Handle promotion offers, that is, non-local tree rewrites.
*
* @param offer The type of rewrite being offered
* @throws XPathException
*/
protected void promoteInst(PromotionOffer offer) throws XPathException {
select = doPromotion(select, offer);
if (offer.action == PromotionOffer.INLINE_VARIABLE_REFERENCES ||
offer.action == PromotionOffer.EXTRACT_GLOBAL_VARIABLES) {
// Don't pass on other requests
action = doPromotion(action, offer);
key = doPromotion(key, offer);
}
// TODO: promote expressions in the sort key definitions
}
/**
* Get all the XPath expressions associated with this instruction
* (in XSLT terms, the expression present on attributes of the instruction,
* as distinct from the child instructions in a sequence construction)
*/
/*@NotNull*/
public Iterator iterateSubExpressions() {
ArrayList list = new ArrayList(8);
list.add(select);
list.add(action);
list.add(key);
if (collationNameExpression != null) {
list.add(collationNameExpression);
}
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
list.add(skd.getSortKey());
Expression e = skd.getOrder();
if (e != null) {
list.add(e);
}
e = skd.getCaseOrder();
if (e != null) {
list.add(e);
}
e = skd.getDataTypeExpression();
if (e != null) {
list.add(e);
}
e = skd.getLanguage();
if (e != null) {
list.add(e);
}
e = skd.getCollationNameExpression();
if (e != null) {
list.add(e);
}
}
}
return list.iterator();
}
/**
* Get the immediate sub-expressions of this expression, with information about the relationship
* of each expression to its parent expression. Default implementation
* returns a zero-length array, appropriate for an expression that has no
* sub-expressions.
*
* @return an iterator containing the sub-expressions of this expression
*/
@Override
public Iterator iterateSubExpressionInfo() {
ArrayList list = new ArrayList(8);
list.add(new SubExpressionInfo(select, true, false, INSPECTION_CONTEXT));
list.add(new SubExpressionInfo(action, false, true, INHERITED_CONTEXT));
list.add(new SubExpressionInfo(key, false, true, NODE_VALUE_CONTEXT));
if (collationNameExpression != null) {
list.add(new SubExpressionInfo(collationNameExpression, true, false, NODE_VALUE_CONTEXT));
}
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
list.add(new SubExpressionInfo(skd.getSortKey(), false, true, NODE_VALUE_CONTEXT));
Expression e = skd.getOrder();
if (e != null) {
list.add(new SubExpressionInfo(e, true, false, NODE_VALUE_CONTEXT));
}
e = skd.getCaseOrder();
if (e != null) {
list.add(new SubExpressionInfo(e, true, false, NODE_VALUE_CONTEXT));
}
e = skd.getDataTypeExpression();
if (e != null) {
list.add(new SubExpressionInfo(e, true, false, NODE_VALUE_CONTEXT));
}
e = skd.getLanguage();
if (e != null) {
list.add(new SubExpressionInfo(e, true, false, NODE_VALUE_CONTEXT));
}
e = skd.getCollationNameExpression();
if (e != null) {
list.add(new SubExpressionInfo(e, true, false, NODE_VALUE_CONTEXT));
}
}
}
return list.iterator();
}
/**
* Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited
* by an expression in a source tree.
*
* The default implementation of this method assumes that an expression does no navigation other than
* the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the
* same context as the containing expression. The method must be overridden for any expression
* where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression,
* and RootExpression (because they perform navigation), and for the doc(), document(), and collection()
* functions because they create a new navigation root. Implementations also exist for PathExpression and
* FilterExpression because they have subexpressions that are evaluated in a different context from the
* calling expression.
*
* @param pathMap the PathMap to which the expression should be added
* @param pathMapNodeSet the set of nodes within the path map
* @return the pathMapNode representing the focus established by this expression, in the case where this
* expression is the first operand of a path expression or filter expression. For an expression that does
* navigation, it represents the end of the arc in the path map that describes the navigation route. For other
* expressions, it is the same as the input pathMapNode.
*/
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) {
PathMap.PathMapNodeSet target = select.addToPathMap(pathMap, pathMapNodeSet);
if (groupBinding != null) {
pathMap.registerPathForVariable(groupBinding, target);
}
if (collationNameExpression != null) {
collationNameExpression.addToPathMap(pathMap, pathMapNodeSet);
}
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
skd.getSortKey().addToPathMap(pathMap, target);
Expression e = skd.getOrder();
if (e != null) {
e.addToPathMap(pathMap, pathMapNodeSet);
}
e = skd.getCaseOrder();
if (e != null) {
e.addToPathMap(pathMap, pathMapNodeSet);
}
e = skd.getDataTypeExpression();
if (e != null) {
e.addToPathMap(pathMap, pathMapNodeSet);
}
e = skd.getLanguage();
if (e != null) {
e.addToPathMap(pathMap, pathMapNodeSet);
}
e = skd.getCollationNameExpression();
if (e != null) {
e.addToPathMap(pathMap, pathMapNodeSet);
}
}
}
return action.addToPathMap(pathMap, target);
}
/**
* Replace one subexpression by a replacement subexpression
* @param original the original subexpression
* @param replacement the replacement subexpression
* @return true if the original subexpression is found
*/
public boolean replaceSubExpression(Expression original, Expression replacement) {
boolean found = false;
if (select == original) {
select = replacement;
found = true;
}
if (action == original) {
action = replacement;
found = true;
}
if (collationNameExpression == original) {
collationNameExpression = replacement;
found = true;
}
if (key == original) {
key = replacement;
found = true;
}
if (sortKeyDefinitions != null) {
for (SortKeyDefinition skd : sortKeyDefinitions) {
if (skd.getSortKey() == original) {
skd.setSortKey(replacement, true);
found = true;
}
if (skd.getOrder() == original) {
skd.setOrder(replacement);
found = true;
}
if (skd.getCaseOrder() == original) {
skd.setCaseOrder(replacement);
found = true;
}
if (skd.getDataTypeExpression() == original) {
skd.setDataTypeExpression(replacement);
found = true;
}
if (skd.getLanguage() == original) {
skd.setLanguage(replacement);
found = true;
}
}
}
return found;
}
/**
* Check that any elements and attributes constructed or returned by this expression are acceptable
* in the content model of a given complex type. It's always OK to say yes, since the check will be
* repeated at run-time. The process of checking element and attribute constructors against the content
* model of a complex type also registers the type of content expected of those constructors, so the
* static validation can continue recursively.
*/
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException {
action.checkPermittedContents(parentType, env, false);
}
public TailCall processLeavingTail(XPathContext context) throws XPathException {
Controller controller = context.getController();
assert controller != null;
GroupIterator groupIterator = getGroupIterator(context);
XPathContextMajor c2 = context.newContext();
c2.setOrigin(this);
c2.setCurrentIterator(groupIterator);
c2.setCurrentGroupIterator(groupIterator);
c2.setCurrentTemplateRule(null);
if (controller.isTracing()) {
TraceListener listener = controller.getTraceListener();
assert listener != null;
while (true) {
Item item = groupIterator.next();
if (item == null) {
break;
}
listener.startCurrentItem(item);
action.process(c2);
listener.endCurrentItem(item);
}
} else {
while (true) {
Item item = groupIterator.next();
if (item == null) {
break;
}
action.process(c2);
}
}
return null;
}
/**
* Get the expression which, on evaluation, yields the name of the collation to be used
* @return the expression that returns the collation name
*/
public Expression getCollationNameExpression() {
return collationNameExpression;
}
/**
* Get (and if necessary, create) the comparator used for comparing grouping key values
* @param context XPath dynamic context
* @return a StringCollator suitable for comparing the values of grouping keys
* @throws XPathException if a failure occurs evaluating the expression that determines the collation name
*/
private StringCollator getCollator(XPathContext context) throws XPathException {
if (collationNameExpression != null) {
StringValue collationValue = (StringValue)collationNameExpression.evaluateItem(context);
assert collationValue != null;
String cname = collationValue.getStringValue();
cname = CollatingFunction.expandCollationURI(cname, baseURI);
return context.getCollation(cname);
} else {
// Fallback - this shouldn't happen
return CodepointCollator.getInstance();
}
}
public AtomicComparer getAtomicComparer(XPathContext context) throws XPathException {
StringCollator coll = collator;
if (coll==null) {
// The collation is determined at run-time
coll = getCollator(context);
}
return AtomicSortComparer.makeSortComparer(coll, keyItemType, context);
}
private GroupIterator getGroupIterator(XPathContext context) throws XPathException {
SequenceIterator population = select.iterate(context);
// get an iterator over the groups in "order of first appearance"
GroupIterator groupIterator;
switch (algorithm) {
case GROUP_BY: {
AtomicComparer comparer = getAtomicComparer(context);
XPathContext c2 = context.newMinorContext();
c2.setCurrentIterator(population);
// TODO: how come this needs a new context and group-adjacent doesn't?
groupIterator = new GroupByIterator(population, key, c2, comparer, composite);
break;
}
case GROUP_ADJACENT: {
AtomicComparer comparer = getAtomicComparer(context);
groupIterator = new GroupAdjacentIterator(population, key, context, comparer, composite);
break;
}
case GROUP_STARTING:
groupIterator = new GroupStartingIterator(population,
((PatternSponsor)key).getPattern(),
context);
break;
case GROUP_ENDING:
groupIterator = new GroupEndingIterator(population,
((PatternSponsor)key).getPattern(),
context);
break;
default:
throw new AssertionError("Unknown grouping algorithm");
}
if (groupBinding != null) {
groupIterator.setGroupSlot(groupBinding.getLocalSlotNumber());
}
if (keyBinding != null) {
groupIterator.setKeySlot(keyBinding.getLocalSlotNumber());
}
// now iterate over the leading nodes of the groups
if (sortKeyDefinitions != null) {
AtomicComparer[] comps = sortComparators;
XPathContext xpc = context.newMinorContext();
if (comps == null) {
comps = new AtomicComparer[sortKeyDefinitions.length];
for (int s = 0; s < sortKeyDefinitions.length; s++) {
comps[s] = sortKeyDefinitions[s].makeComparator(xpc);
}
}
groupIterator = new SortedGroupIterator(xpc, groupIterator, this, comps);
if (groupBinding != null) {
groupIterator.setGroupSlot(groupBinding.getLocalSlotNumber());
}
if (keyBinding != null) {
groupIterator.setKeySlot(keyBinding.getLocalSlotNumber());
}
}
return groupIterator;
}
/**
* Return an Iterator to iterate over the values of a sequence. The value of every
* expression can be regarded as a sequence, so this method is supported for all
* expressions. This default implementation relies on the process() method: it
* "pushes" the results of the instruction to a sequence in memory, and then
* iterates over this in-memory sequence.
*
* In principle instructions should implement a pipelined iterate() method that
* avoids the overhead of intermediate storage.
*
* @param context supplies the context for evaluation
* @return a SequenceIterator that can be used to iterate over the result
* of the expression
* @throws XPathException if any dynamic error occurs evaluating the
* expression
*/
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
GroupIterator master = getGroupIterator(context);
XPathContextMajor c2 = context.newContext();
c2.setOrigin(this);
c2.setCurrentIterator(master);
c2.setCurrentGroupIterator(master);
c2.setCurrentTemplateRule(null);
return new ContextMappingIterator(this, c2);
}
/**
* Map one item to a sequence.
*
* @param context The processing context. This is supplied only for mapping constructs that
* set the context node, position, and size. Otherwise it is null.
* @return either (a) a SequenceIterator over the sequence of items that the supplied input
* item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty
* sequence.
*/
public SequenceIterator map(XPathContext context) throws XPathException {
return action.iterate(context);
}
/**
* Callback for evaluating the sort keys
*/
public AtomicValue evaluateSortKey(int n, XPathContext c) throws XPathException {
return (AtomicValue) sortKeyDefinitions[n].getSortKey().evaluateItem(c);
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("forEachGroup");
out.emitAttribute("algorithm", getAlgorithmName(algorithm));
out.startSubsidiaryElement("select");
select.explain(out);
out.endSubsidiaryElement();
out.startSubsidiaryElement("key");
key.explain(out);
out.endSubsidiaryElement();
out.startSubsidiaryElement("return");
action.explain(out);
out.endSubsidiaryElement();
out.endElement();
}
private static String getAlgorithmName(byte algorithm) {
switch (algorithm) {
case GROUP_BY:
return "group-by";
case GROUP_ADJACENT:
return "group-adjacent";
case GROUP_STARTING:
return "group-starting-with";
case GROUP_ENDING:
return "group-ending-with";
default:
return "** unknown algorithm **";
}
}
}